It is well known that organosilicon-type quaternary ammonium salts immobilized on water-insoluble solid carriers (hereinafter referred to as organosilicon-type immobilized bactericides) have antibacterial activity. The bactericides of this type have been used as antibacterial agents for fiber treatment, as water treatment agents or as antibacterial agents to be incorporated into plastics (see, e.g., JP-A 177284/1987, JP-A 196810/1991 and JP-B 019860/1977). The application of organosilicon-type immobilized bactericides has not yet, however, been proposed in the field of oral hygiene.
In the field of oral hygiene, it is well known that conventional water-soluble quaternary ammonium compounds such as cetylpyridinium chloride or benzethonium chloride can be stably blended into dentifrice (see, e.g., JP-A 85310/1986 and U.S. Pat. No. 5,035,880). There is, however, no disclosure of water-insoluble immobilized bactericides in any literature of this field.
In general, organosilicon-type immobilized bactericides have a cationic character to react with any anionic ingredient, such as a foaming agent or a thickening agent, which is usually used in conventional oral compositions, thereby causing a significant decrease in their antibacterial activity. Further, organosilicon-type immobilized bactericides in particulate form have a tendency to aggregate in an aqueous system, so that these particles can hardly be dispersed, thereby making it difficult to attain uniform blending of these bactericides into an aqueous oral composition. Therefore, when an organosilicon-type immobilized bactericide is used in an aqueous system, it is necessary to devise some means for stabilization of this bactericide.